This application claims the benefit of Japanese Application No. 2000-395631 filed in Japan on Dec. 26, 2000, the contents of which are incorporated by reference.
1. Field of the Invention
The present invention relates to an optical sheet having a plurality of optical sheet members joined, an optical sheet manufacturing system for manufacturing the optical sheet, and an optical sheet cutting machine.
2. Description of the Related Art
Optical sheets including the one realized with a lenticular lens sheet and the one realized with a Fresnel lens sheet are adopted as an optical screen on which an image is projected from an image projector. There is a tendency towards a large optical screen in pursuit of large-screen vision of an image. Accordingly, optical sheets with larger areas are in need.
Among the optical sheets, for example, the optical sheet realized with a lenticular lens sheet is structured to have semi-cylindrical projections successively arranged on the surface thereof. A transparent resin material that is heated and softened is rolled out using a roller member that has numerous female semi-cylindrical molds inscribed on the peripheral surface thereof, whereby the lenticular lens sheet is produced.
However, considerable pressure must be applied in order to produce a thin lenticular lens sheet. When an attempt is made to increase the width of a lenticular lens sheet with the thinness maintained, required pressure becomes so high that the rigidity of a manufacturing unit must be raised markedly. This leads to the high costs of manufacturing.
Therefore, a technology for producing a lenticular lens sheet of a large area at low costs by joining lenticular lens sheets of a predetermined width has been developed.
For example, Japanese Unexamined Utility Model Application Publication No. 64-23042 describes a transmissive screen having a plurality of transparent or translucent resin sheets joined. Adjoining of the plurality of resin sheets is made with resin layers, of which optical property is substantially identical to that of the resin sheets, between the resin sheets. More particularly, the resin sheets are realized with lenticular lens sheets, and the lenticular lens sheets are joined at their depressions.
However, the lenticular lens sheet is, as mentioned above, produced by rotating a roller member and pressing it against a resin material. In practice, it is unavoidable that minute undulations occur on the surface of the lenticular lens sheet whose surface is realized with the repetition of a depression and an elevation.
If lenticular lens sheets each having the undulations are joined as they are, a mismatch caused by the undulations produces an optically adverse effect. Consequently, the joint portions of the lenticular lens sheets are visualized as a streak.
Therefore, there is a demand for a technology that takes account the undulations in optical sheet members and prevents them from producing an optically adverse effect.
Accordingly, an object of the present invention is to provide an optical sheet in which joint portions of optical sheet members will produce almost no optically adverse effect.
Another object of the present invention is to provide an optical sheet manufacturing system optimal for manufacturing of an optical sheet in which joint portion of optical sheet members will produce almost no optically adverse effect.
Still another object of the present invention is to provide an optical sheet cutting machine capable of cutting an optical sheet member optimally for joining that will almost not permit joint portions of optical sheet members to produce an optically adverse effect.
Briefly, according to the present invention, there is provided an optical sheet to be used as a screen on which an image is projected from an image projector. The optical sheet has a plurality of optical sheet members which are joined together with end surfaces thereof, which are orthogonal to major surfaces thereof. The optical sheet members are substantially identical to each other to such an extent that the optical property of each optical sheet member changes cyclically in a first direction over the major surface of the optical sheet member, and that undulations exist in a second direction orthogonal to the first direction. One optical sheet member and the other optical sheet member that are to be joined with the joint surfaces thereof are optical sheets whose optical properties exhibited over the joint surfaces are substantially identical to each other within a predetermined permissible range.
Moreover, according to the present invention, there is provided an optical sheet manufacturing system consisting mainly of an optical sheet cutting machine, an optical sheet joining machine, a reservoir, a conveying machine, and a controller. The optical sheet cutting machine trims an optical sheet member optimally for joining. The optical sheet joining machine joins a plurality of optical sheet members with the edges thereof, which have been cut optimally for joining, met each other. At least one of the optical sheet members cut by the optical sheet cutting machine and the optical sheet produced by the optical sheet joining machine is preserved in the reservoir. The conveying machine conveys optical sheet members among the optical sheet cutting machine, optical sheet joining machine, and reservoir. The controller controls the optical sheet cutting machine, reservoir, optical sheet joining machine, and conveying machine.
Furthermore, according to the present invention, there is provided an optical sheet cutting machine consisting mainly of a platform, an investigating device, a cutting blade, a cutting drive source, and a feeding drive source. An optical sheet member to be cut is placed on the platform, and the platform enables adjustment of a slide position and a turn position on the major surface of the optical sheet member. The investigating device investigates the shape of the surface of the optical sheet member placed on the platform so as to determine a cutting band line along which the optical sheet member is cut. The cutting blade is used to trim the optical sheet member. The cutting drive source drives the cutting blade at the same cutting start position. The feeding drive source moves the cutting blade to change the cutting start position. The platform is used to adjust the slide position and turn position on the optical sheet member so that a path along which the cutting blade is moved by the feeding drive source will agree with the cutting band line determined based on the investigation performed by the investigating device. While the cutting drive source is driving the cutting blade, the feeding drive source moves the cutting blade along the cutting band line. The optical sheet member is thus cut.
The above and other objects, features and advantages of the invention will become more clearly understood from the following description referring to the accompanying drawings.